1. Field of the Invention
The present invention relates to a disc cartridge having a recording disc rotatably enclosed in a disc case.
2. Discussion of Related Art
In a disc cartridge of the type comprising an optical or magnetic recording medium made of a hard disc rotatably enclosed in a hard case of a generally rectangular shape, there is provided a clamp mechanism for preventing rotation of the recording disc when the disc cartridge is not in use. As shown in FIG. 1, the recording disc 4 is rotatably supported in the disc case 1 by rollers 45 and 46 which in turn are rotatably supported on fixed shafts projected on the bottom half 1b of the disc case 1 for rotatably engaging with the outer peripheral edge of the recording disc 4 and a pressing roller 51 rotatably supported on a bent clamp lever 47. The clamp lever 47 is swingably supported on a shaft 50 with the free end 47a of the arm situated in an operating opening 53 defined in part of the side wall 7. The clamp lever 47 is exerted by a spring member 52 so that the pressing roller 51 is biassed toward the rollers 45 and 46 thereby pressing the peripheral edge of the recording disc 4. A slide 56 is slidably provided along the side wall 7 so as to detachably engage with the free end 47a of the clamp lever 47. By this arrangement, when the disc cartridge is not in use, the clamp lever 47 is exerted toward the recording disc 4 by the spring member 52 for holding the recording disc 4 in a clamped manner by the rollers 45 and 46 and the pressing roller 51. On the contrary, when the disc cartridge is mounted on a disc drive apparatus, the slide 56 is moved in a backward direction of the disc case 1 along the side wall by an operating member of the disc drive apparatus whereby the free end 47a of the clamp lever 47 is pressed by the slide 56 so as to rotate the clamp lever 47 toward the side wall 7 for moving the pressing roller 51 to a releasing position away from the recording disc 4.
In the optical recording disc or magnetic recording disc of the vertical magnetization system in which the recording information is recorded at an extremely high density, since each of the recording spots on the disc is extremely small, if small particles of dust are collected on the disc, drop out of the signal or an error in reading the signal may occur. Therefore, dust must be prevented from entering the interior of the disc cartridge. However, according to the conventional disc cartridge having the clamp mechanism as described above, since the clamp lever 47 is adapted to be operated from outside of the disc case through the slide 56, the operating opening 53 is kept opened when the disc cartridge is not in use, therefore dust may easily enter the interior of the disc case 1.